The present invention relates to an arrangement for the automatically controlled changing of the relative rotating position of two shafts in an internal-combustion engine, having at least one camshaft which can be rotated as a function of parameters of the internal-combustion engine relative to a shaft driving it. The arrangement has a wheel which drives the camshaft, carries a first toothing and, by means of a coupling member which is acted upon by an oil circulating system and axially can be shifted at least in two end positions, acts upon a second toothing connected with the camshaft.
It is known to adapt the valve timing of an internal-combustion engine to its rotational speed in order to be able to optimally operate it in a rotational speed range that is as broad as possible. As a result, the torque, the performance, the exhaust gas emission, the idling characteristics and the fuel consumption can be improved.
One possibility of changing the valve timing during the operation of the internal-combustion engine consists of turning, by means of a so-called phase converter, preferably the intake camshaft in its position relative to the crankshaft which drives it. In this case, as a function of the oil pressure, a coupling member is axially shifted which is coaxially surrounded by the wheel driving the camshaft. The coupling member carries two toothings of which at least one is helical and which interact with one corresponding toothing respectively on the camshaft or in the wheel, as known, for example, from the European Patent Document EP-0 335 083.
Phase converters are known, for example, from the European Patent Document EP 0 356 162 or from the already mentioned European Patent Document EP 0 335 083, in which the wheel driving the camshaft has an internal toothing which engages in an external toothing which is assigned to the coupling member acting as a piston which is acted upon hydraulically. The piston carries a second toothing which is constructed as an internal toothing and engages into a corresponding external toothing of the camshaft. In addition, phase converters are known, for example, from the European Patent Document EP 0 245 791 in which the coupling member moved by a hydraulic piston or a solenoid has two external toothings which are axially displaced with respect to one another and of which one engages in an internal toothing of the camshaft while the other engages into an internal toothing of the driving wheel.
All of the above mentioned arrangements have the disadvantage that they require considerable additional space which increases the fitting length of an internal-combustion engine equipped with such an arrangement. Normally, a plane bounds a front-face end of the internal-combustion engine, in which case this plane is formed by the endless drive moving by way of the wheel driving the camshaft. In the known state of the art, either the device projects clearly above this end or, because of the constructional volume of the device, the wheel had to be arranged farther away from the front face of the internal-combustion engine.
It is therefore an object of the invention to avoid the above-mentioned difficulties and thus provide a compact arrangement for changing the relative rotating position of shafts in an internal-combustion engine which requires little space and therefore keeps the overall length of an internal-combustion engine equipped with such an arrangement as short as possible.
This and other objects are achieved by the present invention which provides an arrangement for automatically controlled changing of a relative rotating position of two shafts in an internal-combustion engine, comprising at least one camshaft which can be rotated as a function of parameters of the internal-combustion engine relative to a shaft driving the camshaft and having a second internal toothing. The arrangement includes an oil circulating system, a coupling member and a wheel. The coupling member has a first internal toothing and a second external toothing and is coupled to the oil circulating system so as to be axially shiftable between at least two end positions. The wheel drives the camshaft and has a first external toothing and, via the coupling member, acts upon the second internal toothing of the camshaft. The first external toothing of the wheel interacts with the first internal toothing of the coupling member, and the second internal toothing of the camshaft interacts with the second external toothing of the coupling member.
The arrangement of the present invention permits a compact construction of the phase converter and a simple design of the drive-side end of the camshaft. The compact construction is achieved by the arrangement of the two toothing pairs, which are customary in the case of a phase converter of this type, such that the wheel driving the camshaft carries a first external toothing and that a second toothing connected with the camshaft is constructed as an internal toothing, corresponding toothings of the coupling member constructed as a piston engaging in these two toothings. In this case, the toothings are all essentially coaxially enclosed by the wheel so that no additional space is required that extends in the axial direction.
In an embodiment of the invention, the second toothing is advantageously constructed not directly in the camshaft but in a hollow shaft which is detachably connected with the camshaft and which, at the same time, bounds a space with respect to the camshaft in which the piston can be axially displaced into its end positions.
The problem of axially securing the wheel is advantageously solved by the present invention in that the wheel is axially fixed on the hollow shaft without any impairment of the necessary rotational movement between the wheel and the hollow shaft when the phase converter is actuated. In this case, the wheel may be constructed as a sprocket wheel or a pulley and may be secured by a spring ring acting between the hollow shaft and the wheel or may be screwed together with the hollow shaft in such a manner that the screws, by means of guide sleeves, penetrate oblong holes arranged in the wheel.
The design of the drive-side end of the camshaft, which utilizes only already existing space, is achieved by taking the locking element, which controls the feeding and the removal of oil, out of the phase converter or the camshaft. The locking element may be arranged at any arbitrary point of the internal-combustion engine, for example, in the cylinder head and is also actuated hydraulically.
In a graduated axially extending recess of the camshaft, which is easy to manufacture, a pipe is held which separates two spaces from one another which, according to the position of the locking element, permit the feeding or the removal of oil in the camshaft or the phase converter. The spaces are connected with radial bores of the camshaft which, in turn, interact with pipes which lead into annuli of the locking element constructed as a change-over valve. The radial bores may be arranged at any arbitrary point of the camshaft.
The phase converter projects only slightly beyond the drive-side end of the camshaft and can be mounted as a complete constructional unit. When no phase converter is to be mounted, the camshaft may also be used by the fastening of a changed sprocket wheel. The camshaft, which is normally made of a hard material, requires no toothing or thread.
The arrangement requires only a small amount of oil because only the oil displaced from the chambers adjacent to the piston must be replaced for the shifting of the piston from a first end position into a second end position.
The emptying of the chambers after the switching-off of the internal-combustion engine is avoided by the fact that the oil-carrying pipes are constructed as ascending pipes which prevent an oil return flow.
The actuating circulating system for the arrangement is part of the oil circulating system of the internal-combustion engine. The lubricating circulating system for the camshafts is connected to this actuating circulating system in such a manner that, when the phase converter or the locking element fails, the lubrication is maintained.
The arrangement of the present invention is also quiet in the operation of the internal-combustion engine because there is no mechanical connection between the arrangement and a hood covering it, such as components of the arrangement which are centered in this hood.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.